OK in plain English:
On a trunking system, EVERY radio has to be associated with the system in order to hear the system. When the radio is associated (affiliated) with the system, the radio has to have an ID number. You have to have permission from the person (or company or government agency) in charge of running the system in order to have a radio programmed (by them at a price probably) in order to hear the radio transmissions. They are probably NOT going to give anyone permission to have a radio on their system. IF you where to purchase a radio (usually $1,000's) to use on the system, then you would have to have the proper programming in order for it to work. And (just for the sake of argument) IF you were to somehow come across that programming-let's say not by going through the proper channels (getting permission and programmed by the radio techs)-and your radio ID number shows up in the system (either at the dispatch console or in the computer controlling the system) and if either the dispatch or the computer recognizes that your radio ID is not programmed to be on the system, then the system will "brick" your radio, basically making it as useful as a brick to listen to the system.
The best way to listen to a trunking system is to purchase a trunking capable scanner (ranging $200-$500) and programming it to the system you want to hear. That way you are not breaking any rules.
As far as the ham license goes, there are some areas that have laws against people not having a legitimate reason (firefighter, EMS, volunteer) or a ham license having a scanner or two-way radio in their vehicle. I am not familiar with laws in Canada, but I know here in Tennessee, it is illegal to have the scanner/radio in your car if you're a convicted felon or if you are committing a crime. I have seen police officers question people about having the scanner in their car, even though they were not breaking the law. But in the law it says it is OK to have the scanner/radio in the car IF you have a ham license (which I do and carry a copy of it with me everywhere I go, just in case).
So your best bet is to buy the trunking scanner unless you want to pay $1,000's for a radio, and try and get it programmed legally (which probably won't happen).
I hope this helps you understand what everyone else has been trying to explain to you.